High Performance Glass Scintillators for Nuclear Physics Experiments

High performance scintillator materials are needed for particle identification and measurements of energy and momentum of electromagnetic particles in modern nuclear physics experiments. Achieving high-quality science at nuclear physics facilities requires the measurement of particle energy with excellent calorimeter energy resolution in the momentum range 0.1 – (10-20) GeV/c. Crystals such as lead tungstate (PbWO4) have been used in precision calorimeters but their production is slow and expensive. This Phase I/II project addresses the need for alternative high performance scintillator materials by developing the basis to replace such crystals with scintillating glass that is simpler and faster to produce in large quantities while meeting the desired specifications. Phase I established the fabrication techniques for lab scale production (10-20 blocks) of scintillating glass (SciGlass) with reproducible optical properties and dimensions up to ~10 radiation lengths. Initial measurements with R&D prototypes at particle beam colliders along with simulations indicate that SciGlass has an energy resolution comparable to PbWO4 for block sizes of a comparable number of radiation lengths. The glass samples have excellent optical properties and radiation resistance (no damage up to 1000 Gy electromagnetic and 1015 n/cm2 hadron irradiation, the highest doses tested to date), response time of 20-50 ns, and good transmittance in the near UV domain (78% at 440 nm). The SciGlass insensitivity to temperature is another clear advantage over PbWO4, which has a dependence of about 2-3%/°C and has to be continuously monitored. The feasibility for scaling up the size was demonstrated with the production of 2 x 2 x 40 cm3 blocks. Phase II will establish the new SciGlass developed in Phase I as an electromagnetic calorimeter through definite energy resolution measurements in a particle test beam including a suitable light read-out system. Production capability for larger numbers of uniform SciGlass will be developed to meet the need of large-volume nuclear physics electromagnetic calorimeters. A second objective of Phase II is to demonstrate the production of different SciGlass shapes, e.g., for application in detector barrel regions. The Phase II program is aligned to make SciGlass blocks available to meet the needs of key nuclear physics experiments, e.g., the large-volume calorimeters for the Electron-Ion Collider (EIC) or JLab, that require high performance scintillator material in large quantities on specific schedules. Other SciGlass benefits include reduced time and complexity of manufacturing, resulting in an estimated 80% cost reduction, and increased flexibility in shape and size for the final detector. The ability to manufacture novel high-performance glass scintillators will prove useful not only for electromagnetic calorimeters but also for homeland security applications where such scintillators would significantly reduce the false alarm rate in passive nuclear detection systems and allow for large range of deployment. Fast response time and radiation hard glass ceramics will find use in the scintillator market for security applications as active material for radiation portal monitors, in particular, at ports where cargo screening with large throughput is required.